Fluorescent lamp



April 20, 194 3. w. FoRs-TE ETAL 2,317,265

FLUORESCENT LAMP Filed July 26, 1940 INVENTOR5 WILA/AMJFOERSTE AND EUGENE A. Qt/A lPR/E" Patented Apr. 20, 1943 FLUORESCENT LAMP William Foerste, Pelham Manor, and Eugene A. Quarrie, Scarsdale, N. Y.

Application July 26, 1940, Serial No. 347,590

4 Claims.

The invention relates to luminescent lamps, or rather the so-called fluorescent lamps, embodying a transparent gas-filled envelope coated internally with material fluorescing when a discharge is effected between electrodes in the envelope. Heretofore, this coating has extended entirely around the effective portion of the envelope, which is tubular in form, so that only so much of the light rays from the interior as penetrated the more or less opaque fluorescent material became externally visible.

It is an object of the present invention to increase the eifectiveness of the fluorescent type of lamps by rendering available a greater proportion of the emitted light rays.

A further object of the invention is to increase the normal life of these lamps, and also to improve their operation. v

In carrying out the invention, instead of coating over the entire effective inner surface of the envelope. as heretofore, a portion of this surface is left transparent and uncoated or the coating thereover materially'reduced in density, thereby affording a window more or less transparent through which light rays emitted internally and which do not pass through the body of the coating may pass through in the opposite direction, and thus enhance the value of the lamp to a considerable extent. It affords, moreover, a lamp with directional effect. Provision is also made for increasing the effective surface area coated with fluorescent material to compensate to a large extent for the amount of fluorescing material lost in providing the said window.

In the case of short-length lamps whose life is considerably lessened due to the relatively reduced gas capacity, there is provided a means for supplementing the gas volume so that the life of the lamp is materially prolonged.

To steady the operation of the lamp, there is included in the electrical supply thereto a novel high-tension circuit which embodies an autotransformer with magnetic leakage cores.

The nature of the invention, however, will best be understood when described in connection with the accompanying drawing, in which:

Fig. 1 is a more or less diagrammatic view illustrating the novel fluorescent lamp and circuit modification in the coated surface area, and Fig. 5 is a transverse section therethrough.

Fig. 6 is a transverse section illustrating a modification in the coating arrangement.

Fig. '7 illustrates in transverse section a modification in the manner of increasing the coated surface area.

Referring to the drawing, more particularly Fig. 1 thereof, to designates an envelope of transparent material of the desired shape and length and "designed to retain under a low pressure a rare gas such as argon, neon, etc., or combinations thereof, and associated with mercury, if its color and actinic efiect is desired. Through this gas an electric discharge is arranged to take place as between the electrodes I I and I2, of the self-heating emissive type, which are mounted in the opposite ends of said envelope. A suitable potential is applied to these electrodes to enable the discharge to take place all of which is well understood and forms no particular part of the present invention. However, to steady the discharge and operation of the lamp, it is preferred to utilize the novel circuit arrangement indicated in the drawing, Fig. 1, wherein an auto-transformer l5 has its primary I6 connected with the source of alternating current supply indicated at H, with one of the supply leads grounded as at 3. This primary is included between two magnetic leakage poles or cores I9 and 20, the secondary winding 2! being connected through the leads 22 to the respective electrodes. By this arrangement, the current fiow in the secondary is limited due to the magnetic shunts provided by cores l9 and 20 and stabilization of the discharge secured, while the usual ballast resistance and consequent power loss are also eliminated thereby.

Where the lamps are of relatively short ength, it will be understood that, due to the relatively lessened gas capacity, they will be short-lived and it is preferred, therefore, to provide a reserve supply of gas by increasing the volume of the tube outside of the discharge region. For v example, a reservoir 25 for the gas may be arranged to communicate, through the connection 26 in the vicinity of one of the electrodes, with the interior of the tube to replenish the gas supply as its pressure becomes gradually reduced under the action of the discharge. In addition, there may be contained in the reservoir 25 a gas-evolving substance 21 such as magnesium and calcium carbonate, or organic matter such as certain hydrocarbons (anthracene, oils, gums, resins, etc.) to provide a common gas, in the present instance carbon dioxide, which not only enn'hances the quality of the light but appears to have a tendency to concentrate the discharge at the periphery or in close proximity to the fluorescent coating.

In accordance with the invention, the effective fluorescent or light-radiating surface of such tube is to be coated with suitable fluorescent material such as certain phosphors (zinc-beryllium silicate, cadmium and zinc silicates, etc.) as generally employed over its inner surface; but this material does not extend in. the present instance over the entire surface, or may not be of the same density throughout. Thus, as indicated in Figs. 1 and 3, this material extends merely over the upper, or lower, portion and sides, leaving a window entirely uncovered, in the embodiment shown in Figs. 1-5, through which light emanating from the fluorescent material will be .clearly visible so that the inner fluorescence which, in the usual type of fully-coated interior, was lost to a large extent, is in th novel lamp fully eifective in addition, of course, to the light otherwise radiated in the usual manner. More over, the extreme care required in applying the coating of the usual type of lamp is not necessary, as a more or less dense coating is not obectionable, in fact may improve the light-giving characteristlc.

In Fig. 6 there is indicated a coating which extends entirely over the interior wall surface but has a portion 3| so reduced in density with respect to the normal thickness of the co'ated portion 32 that there will be interstices or a multiplicity of small windows, depending on the granular character of the material, which will transmit to a substantial extent the light rays from the fluorescent inner portion. As in the case of the hereinbefore described embodiment, the coating tapers from a portion of maximum thickness to a portion of minimum'thickness which may terminate at a completely transparent window portion or be of such reduceddimensions or density, as indicated at 3|, Fig. 6, as to not interfere to a serious extent with the transmission of the lightrays. If desired, this reduced density region may be extended entirely'about the tube surface. i e

In view of the reduction of area in the fluorescent materialresulting from the provision of the window, it is desirable to modify the structure of the envelope with a view to increasingthe efl'em tive coated surface. For example, the tube may be of a flattened form as illustrated in Figs. 2 and 3 wherein a large coated surface 33 is indicated opposite the window 34. This particular conformation, furthermore, brings the fluorescent material in closer proximity to the core of the discharge between the electrodes and 38. Or; the surface may be roughened by etching or sand-blasting the same, which not only increases the adhesion of the fluorescent material thereto, but makes for an increase in area.

A further modification is shown in Fig. 4 wherein the interior of the tube is provided with bafiles or transverse projections 31 extending into the interior and over which the coating is applied. Tihs, moreover, locates a larger proportion of the fluorescent material in the region of the core of the discharge, making for a greater conversion and thus enhancing the efllciency of the lamp.

Or, as indicated in Fig. '7, the inner surface may be stippled or corrugated as indicated at 40. To conveniently provide such irregular surfaces for receiving the fluorescent material, the materialbearing surface may be constituted as a separate element from the envelope itself. Thus, as indicated in Fig. 7,'there is fitted into the envelope II a liner member 42 of transparent material which snugly fits therein and bears upon its inner face the desired irregularities 40 for increasing thesurfacearea which receives the fluorescent material.

We claim:

l. A fluorescent lamp comprising a transparent envelope of relatively short length filled with a rare gas and provided' with end electrodes for effecting an electronic discharge therebetween through said gas, and a reservoir foran additional :supply of the rarefled gas located outside the discharge region and permanently in open communication therewith in proximity to one of the electrodes.

2. A fluorescent lamp comprising a transparent envelope of relatively short length filled with a rare gas and provided with end electrodes for flat, transparent envelope filled with a rarefied,

gas and with its inner, light-efiective walls substantially parallel and faced with fluorescent material, and laterally extended electrodes directed substantially across the width of the envelope at its opposite ends for effecting a flattened electronic discharge therein between said electrodes.

4. A fluorescent lamp comprising a flat, transparent envelope filled with a rarefled gas and with its inner, light-effective wall faced with fluorescent material, laterally extended electrodes for effecting a flattened electronic dis-.

charge therein between said electrodes, and a reservoir for an additional supplyof the rarefled gas located at one end of the envelope in open communication therewith in proximity to the corresponding electrode.

WILLIAM FOERSTE. EUGENE A. QUARRIE. 

